Spectroscopic studies of metal high-k dielectrics: Transition metal oxides and silicates, and complex rare earth/transition metal oxides

This paper uses X-ray absorption spectroscopy to the study of electronic structure of the transition metal oxides TiO₂, ZrO₂ and HfO₂, Zr and Hf silicate alloys, and the complex oxides, GdScO ₃, DyScO₃ and HfTiO₄. Qualitative and quantitative differences are identified between dipole allowed intra-atomic transitions from core p-states to empty d*- and s*-states, and inter-atomic transitions from transition metal and oxide 1s states to O 2p* that are mixed with transition metal d*- and s*-states for transition metal oxides and silicate alloys. The complex oxide studies have focused on the O K₁ edge spectra. Differences between the spectral peak energies of the lowest d*-features in the respective O K₁ spectra are demonstrated to scale with optical band gap differences for TiO ₂, ZrO₂ and HfO₂, as well as the complex oxides providing important information relevant to applications of TM oxides as high-k gate dielectrics in advanced Si devices. This is demonstrated through scaling relationships between (i) conduction band offset energies between Si and the respective dielectrics, and the optical band gaps, and (ii) the optical band gaps, the conduction band offset energies, and the electron tunneling masses as functions of the atomic d-state energies of the transition metal atoms.